I use and really like the Sport Dog models. Currently am using the 3200 four dog mdel with a 2 mile range. Works great!! A nice thing about them is the electrodes can be taken out without the unit falling off. Theat way you don't do damage to the neck after prolonged use. They will still give them a zap when needed.

I have used a e collar on pups as young as 6 months. When used correctly it is a great tool. To many people over use them, and in lieu of proper training. Biggest thing is to let them wear them for a couple of weeks before using to get used to them, and not associate them with the shock.